J. F. Brandt
Zeichnung von 1846
1846 J.F. Brandt, Director of the Zoological Museums St. Petersburg, had this first "ideal image"*)icon idealis - meaning: pictured from imagination drawn for his Symbolae sirenologicae I,
"at a time when neither a skeleton nor a good picture of the manati was available to me ... actually only an enhancement of the Pallas Picture"*)translated from Brandt 1867 (see above).

Zeichnung von 1868
1868 this new "ideal picture"*)icon idealis - meaning: pictured from imagination was made under Brandt's supervision, who published it on page 282 of his Symbolae sirenologicae III, now that he had available a skeleton (since 1857) and the Middendorf Picture (since 1867, see above),
"which is mainly based on the contour of the skeleton ... I am convinced that in general this carefully designed figure gives a fair imagination of the shape of the famous Nordic or Steller's Seacow."*)translated from Brandt 1867
This is Brandts original drawing of the skeleton with the dotted contour, which I have enhanced to explain his idea:
drawing of skeleton with contour line